ATTENTION! The is a file with a hole in the middle for you to pause the print and put a weight in. There is also a version with no hole, but it is too light. To do the axles you will need a cut paperclip. You bend over 1 side and put 1 wheel on. Then you put it through the hotwheel. Then you put the other wheel on and bend the paperclip. This is not my video but it may help:
The author hasn't provided the model origin yet.